Don't modify CMake _ROOT variables inside custom Find*.cmake

June 14, 2026

If writing a custom Find*.cmake module, it’s important to avoid modifying the *_ROOT variable corresponding to the Find module’s package. For example, if writing FindMy.cmake, do not modify My_ROOT within FindMy.cmake as that value will be ignored. Instead of modifying the My_ROOT variable, set the output variable say my_root to the modified value. An example of when a My_ROOT variable might be modified is changing the file separator from \ to / on Windows with cmake_path(CONVERT My_ROOT TO_CMAKE_PATH_LIST my_root). Then, feed every “find_*()” command in FindMy.cmake a HINTS ${my_root} argument.